A database of results from a number of short-term assays has been created using chemicals tested by the CGTB. A subsection of this database contains chemicals tested for carcinogenicity by the NCI and the NTP. This database allows the evaluation of each short- term assay with respect to its ability to predict carcinogenesis or other short-term assay results. It also permits studies of the individual assays with respect to inter- and intra-laboratory reproducibility, and the effects of protocol changes on test responses. As a followup on an evaluation of the ability of four short-term tests (Salmonella mutagenicity; L5178Y mouse lymphoma call mutagenicity; in vitro chromosome aberrations in CHO cells; and in vitro sister chromatid exchanges in CHO cells) to predict carcinogenicity using 73 chemicals, an additional 40 chemicals are being examined. These results will be used to determine if the results obtained with the original 73 chemicals were representative of the database as a whole. In addition to examining the qualitative predictivity of the assays, a study has been initiated to examine the predictivity of the assays as a function of the potency of the short-term test and carcinogenicity test responses. More than 300 coded chemicals have been tested for mutagenicity in Salmonella in more than ore laboratory, or at different times in the same laboratory. The inter- and intra-laboratory reproducibility of the assay is being examined, and differences in qualitative responses will be evaluated with respect to possible differences in test protocols. These analyses will lead to an assessment of the ability of short-term genetic toxicity assays to predict rodent carcinogenicity, and to the design of test protocols and strategies for the deployment of short-term tests.